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Session VI, Zinc and Growth in Specific Disease Entities

Zinc and Health: Workshop Summary

Session VI

Session VI, Zinc and Growth in Specific Disease Entities incorporated several themes under one session.  The importance of zinc and its protection against oxidant stress was reviewed through work done in animal models of zinc deficiency.  In these models of increased susceptibility to oxidant stress was measured by hepatic damage, due to particular hepatocellular toxins, as well as due to increased oxidation of lipoproteins. Guided through a series of elegant studies, which were designed to unravel the mechanism for growth failure that is associated with zinc deficiency, it was demonstrated that providing IGF resulted in no benefit in terms of a growth response to the zinc deficient animals.  In a series of clinical and community-based intervention trials with zinc supplementation, it was shown that there was a significant response, both in terms of linear growth and weight gain to zinc supplementation.  A heterogeneity of responses did appear across studies suggesting that the initial nutritional status and initial plasma zinc concentrations of the children contributed to the variation and magnitude in responses. 

The role of zinc in HIV infection was reviewed. Studies looking at associations between plasma zinc concentrations, the severity of HIV infection, and the progression of disease were reviewed and demonstrated that a negative correlation did in fact exist. That is, more severe disease and more rapid progression of disease was associated with lower initial plasma levels of zinc.  Results from zinc supplementation trials in patients with HIV infection have show that zinc can either reduce the severity of HIV infection or supplements actually can contribute to a more rapid progression of HIV.  Data was presented to show how subjects with HIV on AZT who were administered zinc supplements had increased circulating zinc levels, increased zinc associated thymulin levels, and decreased rates of opportunistic infections. However, in a follow up study, a similar benefit of additional zinc supplementation was not demonstrated, but the regimen itself however, may be protective against zinc deficiency. 

Several studies of zinc supplementation in children utilizing the statistical method of pooled analyses were reviewed to evaluate the outcomes of diarrheal severity.  Consistent across studies was the finding that there was a decrease in the severity of diarrheal episodes as well as a decrease in the incidence of diarrheal episodes due to zinc supplementation.  These findings were remarkably consistent in different subgroups with regard to initial anthropometric status, zinc status, age, and sex.  In patients with malaria, substantial reductions in malaria incidence rates were noted in response to zinc supplementation. 

Lastly, results from a meta-analysis study performed on zinc intervention trials for upper respiratory infections were presented. The results of ten studies were pooled and reviewed. Five studies showed a positive benefit of zinc administration and five studies seemed to indicate that there was no benefit of zinc therapy in the reduction of respiratory infections. However, it was noted that substantial heterogeneity existed across the trials, the use of multiple forms of zinc preparations, and lack of objective outcome measures may have contributed to the failure to detect an impact of the therapeutic regimen.